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From d12ac10d3ce10d3e1c9b23aeca397caa74be49d3 Mon Sep 17 00:00:00 2001
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From: Avi Kivity <avi@redhat.com>
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Date: Mon, 5 Sep 2011 11:07:05 +0300
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Subject: [PATCH] qemu_vmalloc: align properly for transparent hugepages and
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KVM
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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To make good use of transparent hugepages, KVM requires that guest-physical
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and host-virtual addresses share the low 21 bits (as opposed to just the low
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12 bits normally required).
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Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions
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to avoid fragmentation.
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Signed-off-by: Avi Kivity <avi@redhat.com>
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Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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(cherry picked from commit 36b586284e678da28df3af9fd0907d2b16f9311c)
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Signed-off-by: Bruce Rogers <brogers@suse.com>
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Signed-off-by: Andreas Färber <afaerber@suse.de>
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---
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oslib-posix.c | 14 +++++++++++++-
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1 file changed, 13 insertions(+), 1 deletion(-)
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diff --git a/oslib-posix.c b/oslib-posix.c
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index 196099c..a304fb0 100644
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--- a/oslib-posix.c
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+++ b/oslib-posix.c
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@@ -35,6 +35,13 @@
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extern int daemon(int, int);
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#endif
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+#if defined(__linux__) && defined(__x86_64__)
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+ /* Use 2MB alignment so transparent hugepages can be used by KVM */
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+# define QEMU_VMALLOC_ALIGN (512 * 4096)
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+#else
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+# define QEMU_VMALLOC_ALIGN getpagesize()
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+#endif
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+
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#include "config-host.h"
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#include "sysemu.h"
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#include "trace.h"
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@@ -80,7 +87,12 @@ void *qemu_memalign(size_t alignment, size_t size)
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void *qemu_vmalloc(size_t size)
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{
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void *ptr;
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- ptr = qemu_memalign(getpagesize(), size);
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+ size_t align = QEMU_VMALLOC_ALIGN;
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+
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+ if (size < align) {
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+ align = getpagesize();
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+ }
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+ ptr = qemu_memalign(align, size);
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trace_qemu_vmalloc(size, ptr);
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return ptr;
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}
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--
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1.7.11.2
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